I'ave done a few more tests and really can't explain what I am seeing. I really hope someone can, or could check on their charger if they are seeing the same thing.

I consistently see my input voltage in increase on the PL8 as the load is applied. I have now seen this using two separate power supplies. I would have expected to see the voltage drop slightly.

With a 10 amp load pulling 20amps from the DLS-55 PS my PL8 reading for voltage goes from 13.65 to 14.01v. Multimeter reading goes from 13.64 to 13.58
When I try to max out the PL8 my PL8 reading for voltage goes from 13.65v to 14.23v at 38amp being pulled.

With a 10 amp load pulling 20amps from a Revolectrix 28amp PS my PL8 reading for voltage goes from 13.85 to 14.11v. Multimeter reading went from 13.83 to 13.70v.

With a 15 amp load pulling 28amps from a Revolectrix 28amp PS my PL8 reading for voltage goes from 13.85 to 14.20v. Multimeter reading went from 13.83 to 13.24v.

When I hook up my 10S charger to the DLS-55 PS my voltage reading on the charger went from 13.6v to 13.7v. , with a 10amp load pulling 24amps. Multimeter reading went from 13.63 to 13.52v.

I really hope someone can explain this and why it seems that the voltage increases with load when using to the PL8? Maybe the mulitmeter is not sensitive enough for spikes, but I would think it should at least follow the same trend of the charger reading.

Again, it would be great if someone could help me out with this or at least confirm that they are seeing a similar situation, or does there voltage remain constant or slightly drop.

I wonder if the PL8 is reporting the voltage at its input terminals or the voltage it estimates to be present at the PS output terminals?

It is possible it is estimating the voltage drop in the input leads based on the measured input current and adding this to the measured input voltage to estimate the PS output voltage. If that is the case your results show that at 20A input current the voltage reported goes up by about 400mV which would correspond to an estimated lead resistance of 20mOhm. 10awg wire is about 1.2mOhm per foot so for the charger to be estimating 20mOhm it must think it has 16ft of lead! Oh well, there goes that theory.

I am also curious as to the logic the charger uses in order to flag this as an error. Before this gets written off as a power supply error the firmware developers need to double check their error logic and validate it against the power supply output.

I recall another charger manufacturer having problems with a certain brand of power supplies a while back and they were able to make a firmware change to correct the problem.

PL8 and IOTA PSU

Hi:

I know there is a lot of discourse going on about using the PL8 in tandem with IOTA Power Supplies. I also realize that IOTA is a popular low-cost brand. Based on the test results presented in this forum, we speculate the following. It is important to note that these are not final conclusions; hence, I term this speculation. But we thought it good to let everybody know we will be working on this issue in coming days/weeks.

It is also important to note that we make no claims or representations regarding the quality of the IOTA or other Power Supply units. At this point, we are merely speculating what we think could be happening based on the reports within this thread.

1) The Supply Noise safety code and the charger pinching back is due to wide voltage range fluctuation on the input. Currently, the PL8 is designed to elicit this particular safety code when the measured voltage fluctuation is 2V or more.

2) Why is this safety feature built in? It's built in to prevent wires and connectors from melting or catching fire in the event that someone uses small wire to connect power, poor connectors, or loose connections. Yes, pulling 50A you definitely need a solid connection and we would not feel comfortable putting the PL8 on the streets without this safety feature. You may not see this issue at lower charge currents because the PSU output voltage is more stable. You may not experience this with other chargers which do not have this built in safety feature.

3) Another good piece of information supplied in this thread is that the IOTA will cause the PL8 to elicit low voltage input safety code unless the low voltage cutoff is set down to the lowest possible setting of 10A for Power Supply setup. This is another indication that the line voltage regulation of this power supply is outside of the PL8 threshold of 2V.

4) These things being said, we will take a look at the IOTA supplies and see if we can relax the threshold for this safety code. First we have to obtain one of the DLS models as we do not currently own one.

5) Another factor that may play into this is the ramp up speed of the PL8. If the safety code is tripping right away, or you hear surging of the fans as soon as the current ramp up begins, this is an indication that the supply output is dropping below the 12V regulator feeding the fans. When the PSU begins to catch up, it might cause the fans to over-surge a bit as the voltage increases rapidly back up toward 12v regulation.

6) While we realize it may not be the "preferred" solution, we do think that adding a large capacitor across the output of the PSU will help smooth the voltage transients and depressions and improve or eliminate the problem. One customer has attempted testing using a 10,000 UF and noticed an improvement. We think a 22,000 UF, 35V-50V, low ESR capacitor might help the situation substantially.

7) With regard to why the PL8 is measuring the voltage at the input higher than a DVM. This is explained by the fact that the DVM is heavily averaging the voltage readings while the PL8 measures instantaneous voltage. When a PSU is attempting to regulate the output the typical response is for the voltage to drop down below the intended regulated voltage and then as it recovers, it will tend to over-shoot the voltage it is attempting to maintain. How tightly voltage line regulation is maintained over the normal changes in current being drawn from the supply depends on many design factors. Generally speaking, the tighter the line regulation, the higher the cost of the device and the faster it reacts to rapid changes in current. The PL8 will tax the capabilities of power supplies in general, not only because it is high current, but because it ramps up farely quickly (in manual charge mode), and because during the course of charging, the duty cycle is not 100%. Precise voltage measurements are taken during "quiet times" when the PWM of the unit actually shuts down and little or no current is delivered to the battery.

8) So, when we get an IOTA PSU in our hands, we will scope it, we will determine if a firmware solution is feasible, and we will keep the users in this thread apprised with our results. In the mean time, if customers with this particular issue have the time, skills, and inclination, I think the following capacitor available at Digikey could provide immediate relief while we continue the investigation on our end for the best solution. It might be that a large capacitor in tandem with a firmware change could be the most effective resolution when using this particular power supply or others of a similar class. There is no downside to smoothing out the voltage transients with a capacitor. We also make no representations or claims regarding the installation of this or similar capacitors without additional research on our end. I am merely providing this information as something that MAY work. One last comment; should you attempt to install a capacitor, make sure your wire is good quality, probably 16AWG or larger, and having solid connections between the poles of the capacitor and the PSU terminals. Also be certain to observe the polarity + to + and - to - or you will surely see a big bang and a lot of smoke.

5) DLS - 55 series M, 12 volt, 55 amp (DLS - 55 M)
This model and the DLS-45m are very popular for use
in bow fishing for power up and maintaining batteries for
a trolling / thruster motor.
These are also popular with automotive technicians for
use in programming the computers in a car.
When the included high-voltage plug is inserted into the
jack on the top of the charger it outputs a continuous
14.2 volts d.c. $ 155.00 each
740 watt output, image link: DLS - 55
Shipping on this charger using the PayPal cart is a flat $ 15.00.

Thanks for your help on this, I am really glad FMA is looking into this. It just continues to show that FMA is a quality company with quality products.

I also wanted to comment on the FMAís commitment to safety. For me, my confidence in FMA products being able to safely charge packs is one of the main reasons why I am a FMA customer (I have a PL8, 10s and two 4sís). When charging lipoís, I personally wanted to get the safest and best chargers out there, and thatís why I went for FMA products.

Thanks again, and if there is anything I can do to help out, please just ask. I have two more capacitors on order to try out, a 20,000 uF and 30,000uF. Iíll report back on what I find.

It seems that the PL8 charger is bringing alot of us into a new area of modelling - how to feed a high power charger. Perhaps a sticky thread with some guidelines of what to look for in powering this beast (or pair of beasts) using 12V or 24V, either battery or PSU, and maybe some recommended units that have passed FMA testing. . .

Post # 11 which is on the first page of this thread has links to server power supplies which I have used. The hp ESP114s are the most bang for the bucks . I have less than $50 in my pair counting shipping leads and connectors.

FMA is not going to get into recomending power supplies I do not believe that I have get to hear or read of anyone having serious issues with server power supplies.

Meanwell power suppies are excellent and David at progressiverc.com has a selection often ,just depends on what he can find at decent prices.